NEW DELHI — It had all the makings of a disaster movie: more than half a billion people without power. Trains motionless on the tracks. Miners trapped underground. Subway lines paralyzed. Traffic snarled in much of the national capital.
On Tuesday, India suffered the largest electrical blackout in history, affecting an area encompassing about 670 million people, or roughly 10 percent of the world’s population. Three of the country’s interconnected northern power grids collapsed for several hours, as blackouts extended almost 2,000 miles, from India’s eastern border with Myanmar to its western border with Pakistan.
For a country considered a rising economic power, Blackout Tuesday, which came only a day after another major power failure, was an embarrassing reminder of the intractable problems still plaguing India: inadequate infrastructure, a crippling power shortage and, many critics say, a yawning absence of governmental action and leadership.
India’s coalition government, already battered for its stewardship of a wobbling economy, again found itself on the defensive, as top ministers could not definitively explain what had caused the grid failure or why it had happened on consecutive days.
Theories for the extraordinarily extensive blackout included excessive demands placed on the grid from certain regions, due in part to low monsoon rains that forced farmers to pump more water to their fields, and the less plausible possibility that large solar flares had set off a failure.
By Tuesday evening, power had been restored in most regions, and many people in major cities barely noticed the disruption because localized blackouts are so common that many businesses, hospitals, offices, and middle-class homes are equipped with backup diesel fuel generators.
But that did not prevent people from being furious, especially after the government chose Tuesday to announce a long-awaited Cabinet reshuffle in which the power minister was promoted to take over the home ministry, one of the country’s most important positions.
‘‘This is a huge failure,’’ said Prakash Javadekar, a spokesman for the opposition Bharatiya Janata Party. ‘‘It is a management failure as well as a failure of policy. It is policy paralysis in the power sector.’’
For millions of ordinary people, Tuesday brought frustration and anger; for some, there was fear. As nighttime arrived, Kirti Shrivastava, 49, a housewife in the eastern city of Patna, said power had not been restored in her neighborhood.
‘‘There is no water, no idea when electricity will return,’’ she said. ‘‘We are really tense.’’
Tuesday also brought havoc to India’s railroad network, one of the busiest in the world. Across the country, hundreds of trains were stalled for hours before service resumed.
Sushil Kumar Shinde, the power minister, who spoke to reporters in the afternoon, did not specify what caused the grid breakdown but blamed several northern states for consuming too much power from the national system.
‘‘I have asked my officers to penalize those states which are drawing more power than their quota,’’ said Shinde, whose promotion was announced a few hours later.
Surendra Rao, formerly India’s top electricity regulator, said the national grid had a sophisticated system of circuit breakers that should have prevented such a blackout. But he attributed this week’s problems to the bureaucrats who control the system, saying that civil servants are beholden to elected state leaders who demand that more power be diverted to their regions — even if doing so threatens the stability of the national grid.
‘‘The dispatchers at both the state and the regional level should have cut off the customers who were overdrawing, and they didn’t,’’ Rao said. ‘‘That has to be investigated.’’
India’s power sector has long been considered a potentially crippling hindrance to the country’s economic prospects. Part of the problem is access; more than 300 million people in India still have no electricity.
But India’s power generation capacity also has not kept pace with growth; in March, for example, demand outpaced supply by 10.2 percent, according to government statistics.